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数学表达式解释器

示例需求

1. 支持数字、变量、加减乘除运算
2. 支持函数调用（如 max(2,3)）
3. 能够处理嵌套表达式（如 (x + 5) * max(y,10)）

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完整代码实现

#include <iostream>
#include <memory>
#include <unordered_map>
#include <vector>
#include <sstream>
#include <cctype>
#include <cmath>// ====================== 解释器核心组件 ======================
class Context {
public:std::unordered_map<std::string, double> variables;double getVariable(const std::string& name) const {auto it = variables.find(name);if (it == variables.end()) throw std::runtime_error("Undefined variable: " + name);return it->second;}
};class Expression {
public:virtual double interpret(const Context& ctx) const = 0;virtual ~Expression() = default;
};// ====================== 终结符表达式 ======================
class Number : public Expression {double value;
public:Number(double v) : value(v) {}double interpret(const Context&) const override { return value; }
};class Variable : public Expression {std::string name;
public:Variable(std::string n) : name(std::move(n)) {}double interpret(const Context& ctx) const override {return ctx.getVariable(name);}
};// ====================== 非终结符表达式 ======================
class AddExpr : public Expression {std::unique_ptr<Expression> left, right;
public:AddExpr(Expression* l, Expression* r) : left(l), right(r) {}double interpret(const Context& ctx) const override {return left->interpret(ctx) + right->interpret(ctx);}
};class MultiplyExpr : public Expression {std::unique_ptr<Expression> left, right;
public:MultiplyExpr(Expression